Brown Recluse Spider, Loxosceles Reclusa Gertsch & Mulaik (Arachnida: Araneae: Sicariidae)1 G
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EENY299 Brown Recluse Spider, Loxosceles reclusa Gertsch & Mulaik (Arachnida: Araneae: Sicariidae)1 G. B. Edwards2 Introduction I called the Florida Poison Control Network to confirm these numbers, and was cited 182 total cases and 96 in the The brown recluse spider, Loxosceles reclusa Gertsch & Tampa region. The actual numbers are less important than Mulaik, is frequently reported in Florida as a cause of the fact that a significant number of unconfirmed brown necrotic lesions in humans. For example, in the year 2000 recluse spider bites are reported in the state every year. Yet alone, Loft (2001) reported that the Florida Poison Control not one specimen of brown recluse spider has ever been Network had recorded nearly 300 alleged cases of brown collected in Tampa, and the only records of Loxosceles recluse bites in the state; a subset of 95 of these bites was species in the entire region are from Orlando and vicinity. reported in the 21 counties (essentially Central Florida) A general review of the brown recluse, along with a critical under the jurisdiction of the regional poison control center examination of the known distribution of brown recluse in Tampa. and related spiders in Florida, seems in order at this time. Distribution Loxosceles reclusa was described by Gertsch and Mulaik (1940) from Texas. At the time of the first revision of the genus Loxosceles in the Americas (Gertsch 1958), the known distribution ranged from Central Texas to southern Kansas, east through middle Missouri to western Tennessee and northern Alabama, and south to southern Mississippi. Gorham (1968) added Illinois, Kentucky, and northern Georgia. Later, he added Nebraska, Iowa, Indiana and Ohio, with scattered introductions in other states, includ- ing Florida; his map indicated a record in the vicinity of Tallahassee (Gorham 1970). Weems and Whitcomb (1975) noted that, “on many oc- Figure 1. Female brown recluse spider, Loxosceles reclusa Gertsch & casions specimens have been inadvertently brought into Mulaik. Florida in trucks and automobiles, hidden in luggage, Credits: Jeffrey Lotz, Division of Plant Industry 1. This document is EENY299, (originally published as DPI Entomology Circular 406), one of a series of the Entomology and Nematology Department, UF/IFAS Extension. Original publication date August 2003. Revised August 2015. Visit the EDIS website at http://edis.ifas.ufl.edu. This document is also available on the Featured Creatures website at http://entnemdept.ifas.ufl.edu/creatures/. 2. G. B. Edwards, Florida Department of Agriculture and Consumer Services, Division of Plant Industry; UF/IFAS Extension, Gainesville, FL 32611. The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office. U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension. boxes, and various commercial cargoes, but to date it In summary, the verified records of brown recluse and appears to have been unsuccessful in establishing breeding related spiders in the state are limited to the following eight populations in Florida.” It is unfortunate that they did not out of 67 Florida counties: Alachua, Bay (Callaway), Dade document these alleged records, as this comment is not (Lemon City), Duval (Jacksonville), Jefferson (Monticello), completely in accord with the following reference. Leon (Tallahassee), Orange (Orlando), and Osceola (Runnymede). The more northern counties (Alachua, Bay, An updated revision of the genus by Gertsch and Ennik Duval, Jefferson, and Leon) were all isolated records of the (1983) reported a few records from Arizona, California, native brown recluse, Loxosceles reclusa, whereas the more Colorado, Florida, Maine, Minnesota, New Jersey, New southern county records (Dade, Orange, and Osceola) were Mexico, New York, North Carolina, Wyoming, and of the introduced Mediterranean recluse, Loxosceles rufes- Tamaulipas (Mexico) the reported Ontario (Canada) record cens. The Alachua, Dade, and Jefferson county records were in this publication subsequently proved to be a specimen interceptions of single specimens. The Bay, Duval, Leon, of Loxosceles rufescens (Dufour); R. Vetter, personal Orange, and Osceola county records were infestations in communication, 2001. Most of these peripheral records one or two buildings. There is no evidence to support either were interceptions of one or two specimens, not evidence the notion that a widespread population of brown recluse of established populations. The Florida records consisted spiders exists in Florida or that there are numerous intro- of two specimens, one each from Alachua (collected 10 ductions of brown recluse into the state. Therefore, there January 1969) and Jefferson (Monticello, collected 21 is no reason to assume that frequent interactions between August 1968) counties, and both were taken from inside brown recluse and humans occur in Florida. Subsequent to automobiles. Subsequently, a sailor was bitten on the hand the original publication of this work (as a DPI Entomology by a male brown recluse in the cargo hold of a naval ship Circular), Loxosceles rufescens was found in a warehouse in in Jacksonville, in March 1986. This ship had just arrived Escambia County, Florida; and Loxosceles laeta (Nicolet), from North Carolina, where it had loaded supplies. To the Chilean recluse spider, was found in a home in Polk date, this appears to be the only verified case (the actual County, Florida (Edwards 2002a). causative agent of a bite captured and identified) of brown recluse spider bite in Florida [due to complicating factors, I have personally identified several hundred Florida spiders medical personnel familiar with this case even questioned submitted for identification by the public, and only one the veracity of this one alleged bite]. specimen (the Bay County record) proved to be a brown recluse spider. In addition, I have seen thousands of Florida Within the last two years, single buildings (in Callaway, spiders submitted by professional biologists and inspectors, Jacksonville and Tallahassee) have been found to contain with only the few specimens mentioned above proving to populations of Loxosceles reclusa (Edwards 1999, 2000, be members of the genus Loxosceles. It appears obvious to 2001). There is reason to believe that all three of these re- me that the chance of interaction between brown recluse cords are the result of movement of infested materials from spiders and people in Florida is close to nil, agreeing with other states, so it is entirely possible that the infestations are Vetter’s (2000) assessment of reported brown recluse bites restricted to these buildings and can be eliminated. Such outside the natural range of the spider. Medical personnel was the case with an infestation of the similar Loxosceles should, therefore, consider a multitude of more likely rufescens found in Orange County (DPI records from causes (see below) before diagnosing and treating a necrotic Orlando: 28 January 1982, 4 January 1983 and 18 August wound as a brown recluse bite. 1986) in a single building; the spiders were subsequently eradicated. Description The only other records of Loxosceles rufescens occurring The description is taken from Gertsch (1958). Adults of in Florida are a few juvenile spiders in buildings in both sexes are similar in appearance and size, ranging from nearby Osceola County (Runnymede; Banks 1904) and about 7 to 12 mm in body length. Adult females average one juvenile specimen from Dade County (Lemon City; slightly larger, about 9 mm compared to about 8 mm for Gertsch 1958). This cosmopolitan species is probably native adult males. The carapace is pale yellow to reddish brown, to the Mediterranean region, and is sometimes called the with a dusky brown patch just in front of the median groove Mediterranean brown spider or Mediterranean recluse. It (which is encompassed by a narrow, dark line); this patch is has been recorded from a number of localities across the united to the front of the carapace by dusky brown stripes. U.S., particularly in larger cities, where it is transported by In total, these markings appear in the form of a violin. In commerce (Gertsch and Ennik 1983). addition, three dusky patches may occur along the margin Brown Recluse Spider, Loxosceles reclusa Gertsch and Mulaik (Arachnida: Araneae: Sicariidae) 2 on each side. The sternum is yellowish, with other ventral the brown recluse (Edwards 1983). The male palp length body parts of the cephalothorax darker reddish brown. of Loxosceles reclusa is under 4 mm, considerably less than the superficially similar crevice spider. Another difference between the two species is that Loxosceles reclusa has six eyes composed of three isolated pairs (dyads), whereas Kukulcania hibernalis has eight eyes all clumped together in the middle front of the carapace. Figure 2. Detail of the carapace of the brown recluse spider, Loxosceles reclusa Gertsch & Mulaik, showing the dark fiddle-shaped marking often used to identify this spider. Credits: James L. Castner, University of Florida The legs are slender and dusky orange to dark reddish brown. They are numbered front to back with Roman numerals (I, II, III, IV). In females, the leg length formula, Figure 4. Male southern house spider, Kukulcania hibernalis (Hentz). longest to shortest, is II, IV, I, III, typically with leg II being Credits: Jeffrey Lotz, Division of Plant Industry over 18 mm in length, and leg III about 15 mm, the other two pair intermediate in length. The male leg formula is II, I, IV, III, with leg II over 24 mm and leg III about 17 mm. The abdomen of both sexes is tan to brown, but it may appear darker if the spider has recently fed.